1. Field of the Invention
The instant invention relates to methods of and apparatus for simulating ultrasonic pulse echoes. More particularly, the present invention relates to methods of and apparatus for simulating ultrasonic pulse echoes, in order to test ultrasonic flaw detectors.
2. Technical Considerations and Prior Art
In order for ultrasonic flaw detectors to be reliable, it is necessary to test and calibrate the flaw detectors periodically to insure that the detectors have both horizontal and vertical linearity. If a flaw detector gives erroneous readings because of its own defects, it is impossible to determine whether or not an article or material being tested has flaws. Consequently, reliability of the flaw detector is of utmost importance in achieving reliability of the article or material being tested.
The usual method of testing and calibrating an ultrasonic flaw detector is to couple the transducer of the detector with standard test specimens, which have given thickness and sonic speeds. However, this procedure is rather time consuming and can be inaccurate, in that the tester must hold the transducer in contact with the test sample while the detector is being monitored.
Testing and calibrating detectors so that the detectors will correctly recognize flaws in an article consumes a great deal of time. This usually involves moving the transducer along a standard test sample having a plurality of holes positioned at different depths. The resulting signals decline logarithmically in amplitude and are then raised in amplitude by the flaw detector to a common level, in order to establish the linearity of the flaw detector. This test may take 10 to 15 minutes, and requires considerable manual effort.
When using the standard specimen approach, it is quite difficult to pin-point just where defects occur in the circuitry of the flaw detector. This test only indicates that there is something wrong with the flaw detector. However, the particular portion of the circuit in which the error occurs can not readily be identified, because the tester is not able to probe separate portions of the flaw detector circuit.
For these reasons, it is necessary to have a more convenient, more reliable and faster way of calibrating and testing ultrasonic flaw detectors.